Radio receiving apparatus



Feb. 25, 1941. a n- JR 2,233,113

RADIO RECEIVING APPARATUS Filed Aug. 25, 1958 3 Sheets-Sheet 1 5 77INVENTOR q 7 BYRoM J, SMU'H C/iu z.

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FIG, 7, BY

ATTORNEY Feb. 25, 1941. a J n- JR 2,233,113

RADIO RECEIVING APPARATUS INVENTOR BYRoM J. SMITH @Z/Qw' ATTORNEY Feb.25, 1941. SMITH, JR 2,233,113

RADIO RECEIVING APPARATUS Filed Aug. 25, 1938 :s sheets-sheet s INVENTORBYROM J. SUITH BY Gi A flQA/ ATTORNEY Patented Feb. 25, 1941 UNITEDSTATES PATENT OFFICE RADIO RECEIVING APPARATUS Byrom J. Smith, Jr.,Indianapolis, Ind., assignor to Fairbanks, Morse & (30., Chicago, 111.,a. corporation oi Illinois My invention relates to radio receivingapparatus, and more particularly to improvements in switching means forthe control of motor driven tuning mechanisms used in connection withradio receivers.

The principal purpose of my invention is to provide improved switchmeans of pre-selector type for controlling the operation of an electricmotor that serves to drive, or effect the adjustment of variablecondensers or other tuning media, whereby the receiver may be quicklyand accurately tuned to the signal frequency of any one of a number ofpredetermined transmitting stations by the actuation of a selectorswitch,

5 which, if desired, may be located remote from the receiver.

An object of my invention is attained in the provision of an improvedcontrol unit for the motor that drives the tuning condensers, comprisinga bank of individually adjustable commutator elements which are rotatedby the driving motor in unison with said condensers. The motor isadapted to be circuited with, and controlled by, any selected one ofthese commutators,

each of which is identified with a desired transmitting station byeffecting an angular adjustment thereof relative to the bank of tuningcondensers. An important object of the present invention is directed tothe provision of a switch unit of this character which is compact,requiring but small mounting space, and wherein the individualcommutators are adapted to be pre-set by a simple adjusting operationthat can be readily and quickly accomplished by the user.

These and other objects and advantages will more readily appear from thefollowing detailed description of a preferred exemplary embodiment ofthe invention, and from the accompanying drawings, Fig. 1, of which is aside sectional view through the chassis of a radio receiving unit,showing a preferred arrangement of the tuning condensers, driving motor,and preselector motor control organization; Fig. 2 is an enlarged sidesectional View of the motor control organization;

Figs. 3 and 4 are sectional views taken at lines 33 and 4-4,respectively, of Fig. 2; Fig. 5 is a quarter-sectional side view ofpaired contact discs; Fig. 6 is an exploded view of an adjustablecommutator element, these members comprising parts of the motor controlorganization; Fig. 7 is a plan view of a key or locking element used foreifecting an adjustment of the commutator elements, and Fig. 8 is askeleton view showing, diagrammatically, the wiring arrangement of the55 control organization.

Referring now by characters of reference to the drawings, in Fig. 1numeral I0 denotes a horizontal shelf or the equivalent in the chassiscasing of a radio receiver, the front and rear walls of which casing areindicated at H and [2, respectively. Mounted forwardly on shelf [0 is abank of tuning condensers l3, of conven tional type, having a commoncontrol shaft I 4. Suitably keyed to the condenser shaft near itsforward end is a gear l5 that meshes with a pinion IS on a countershaftH. A sheave l8 on shaft I1 is operatively connected by a suitable beltor cord l9 to a power shaft 20 that extends parallel to shafts l4 andIT. The forward end of shaft 20 projects through the front panel 2| ofthe receiver cabinet and carries a manipulating knob 22 which may beused when it is desired to tune the receiver by hand and, as willhereinafter appear, to effect an adjustment of the station selectingmeans. A reversible electric motor 23 of suitable type and construction,0011- nected to shaft 20 at its rear end through gear 24 and pinion 25,provides power for effecting socalled automatic tuning of the receiver.It will be noted that the power transmission means operativelyconnecting condenser shaft l4 and motor 23, namely the belt drive l9 andthe gear sets l5-l6 and 2425, are of speed reducing character so thatmotor 23 functions to drive the condenser shaft at a relatively lowspeed.

A control unit for motor 23, embodying the essential features of thepresent invention, is indicated generally at 30. This unit comprises aframe having opposite end plates 3| and 32 of generally rectangularshape (see Fig. 3), secured together in the formation of a rigidstructure by means of tie rods 33. The top, bottom and sides of theframe structure are substantially open so that the interior functioningmembers of the unit are easily accessible. If desired, a suitableremovable casing or enclosure (not shown) for the unit may be provided.The end plates 3|, 32 have in-turned feet 34 for securement as by screws35 to the shelf I0. A rotatable shaft 36 extends centrally through theframe and has its ends journalled in the end plates 3|, 32. The controlunit is preferably positioned in the chassis structure so that the shaft36 is disposed in axial alignment with the condenser shaft I4, enablingdirect interconnection of these shafts by a simple coupling member. Aprefered type of coupling, appearing in Fig. 1 is sufiiciently flexibleas to permit of limited mis-alignment of the shafts l4 and 36, yetmaintains them in constant phase relationship at all times. -As will behereinafter more readily understood, it is necessary to the properoperation of the control unit to have the two shafts rotate conjointlyand .without angular displacement of one relative to in Fig. 5, and aunitary, adjustable contact ring which is made up of the partsillustrated in Fig. 6. The number of commutator assemblies provided maybe varied to suit the manufacturer, and will depend upon the number oftransmitting stations desired to be preselected for so-called pushbutton or automatic tuning. Thus, a control unit embodying eight of theadjustable commutator assemblies, to be hereinafter described in detail,enables the user to tune in any one of eight preselected transmittingstations merely by actuating a switch identified with the desiredstation. This number will, in most instances, be sufficient to meet therequirements of the average user. By virtue of the improved arrangementherein set forth the manufacturer may readily vary the scope of thecontrol unit by in creasing or diminishing the number of commutatorassemblies, and these are constructed to permit of compact relativedisposition so as to minimize the size of the unit.

Describing now the contact members shown separately in Fig. 5, numeral4| denotes a thin disc of resilient metal having a central opening 42for the reception of shaft 38. In assembly, disc 4| is intended to be inelectrical communication with shaft 38, and to insure positive contactbetween these members disc opening 42 is made slightly smaller than theshaft, short radial slots in the disc permitting the adjacent metal toyield sufliciently to accommodate and tightly embrace the shaft when thedisc is forced thereon. The marginal portion of disc 4| is bentangularly as indicated at 43, so as to effect peripheral contact withthe side face of a contact ring 44. Disc 4| is provided with openings45, disposed diametrically on opposite sides of its center for thereception of rods 48 and short insulating sleeves 41 which precludeelectrical communication between the disc and said rods.

A second contact disc 48, similar in shape and contour to disc 4| isprovided with an insulating hub portion 49, preferably molded thereto,the hub 49 serving to preclude electrical communication between disc 48and shaft 38, and also serving as a bearing for the adjustablecommutator ring, hereinafter described. In assembly disc 48 is intendedto be electrically connected to rods 48, and for effectuating thispurpose the disc 48 is provided with suitably disposed openings 50 forthe rods, the adjacent disc metal engaging the rods in the same mannerthat discs 4| engage shaft 38, previously described. The marginalportion of disc 48 is bent for peripheral contact with the confrontingside face of contact ring 5|. Rods 48 are secured at 52 to a contactdisc 53 which is fixedly mounted on shaft 38 through the agency of a hubportion 54 that serves to insulate disc 53 from the shaft. It will nowappear that, in

assembly, disc 53 is electrically connected to each of the discs 48 bymeans of rods 48, and shaft 38 is electrically connected'to each of thediscs 4|, the two circuits being completely insulated from each other.All of the contact discs 4|, 48 and 53 are locked against relativerotation by rods 48, and the entire assembly thus far described islocked to the shaft by means of a key 55, the component parts being heldtogether between a shoulder 58 on the shaft and an end plate 81 whichmay be press-fitted on the shaft, or secured thereto in any otherdesired manner.

The adjustable members of the commutator assemblies embody the partsbest appearing in Fig. 6, and each includes the contact rings 44 and 5|and an intermediate insulating body portion 58. The rings 44 and 8| areidentical and each is characterized by an outer peripheral edge 59 thatextends slightly less than half the circumference of the ring, orthrough an angle of approximately 178 degrees, such edge extendingradially beyond the complemental edge 88. A shoulder 8| is formed at oneside of the ring where the edges 59 and 88 meet, and diametricallyopposite the shoulder 8| there is formed a marginal recess 82, thepurpose of which will hereinafter appear. In assembly the rings 44 and5| are arranged in coaxial, spaced-apart relation, with their so-calledhigh margins 58 disposed at opposite sides of the composite structure,the recesses 82 being in registration and the shoulders 8| beingseparated by an opening or gap 83 (Fig. 4), approximately one degree incircumferential extent. The body por tion 58 preferably consists of aninsulating plastic, such as Bakelite, die-cast in place between therings 44 and 5| and serves to unify the assembly and to insulate therings from each other. As will be seen from Fig. 6, the body member 58has rim portions 84 that overlie the reduced marginal edges 88 of therings, and an inner flange or hearing part 85. A marginal recess 88registering with the ring recesses 82 is formed in the body member 58.Each of the ring assemblies previously described is mounted on one ofthe hub members 48, and is closely fitted thereto so that a relativelytight juncture occurs at the mating surfaces 81 and 88, respectively, ofeach hub member 41 and its associated ring assembly. The connectionbetween these parts should be sufficiently tight to prevent unintendedslippage therebetween, since under normal operation the contact ringshould turn with the shaft 38 as though it were integral therewith, yetnot so tight as to preclude angular adjustment of the ring relative tothe hub member, accomplished in the manner hereinafter explained.

Each of the commutator assemblies is provided with a resilient contactfinger or brush 10, an additional finger ll of similar type beingprovided for contact with disc 53. These contact fingers extendtransversely of shaft 38 from an elongated insulating base 12 thatbridges the frame plates 3|, 32, the fingers being provided withU-shaped contact terminals 13 that engage the peripheral margins of theadjustable ring assemblies and disc 53 at points vertically below shaft38. The opposite ends of the contact fingers are provided with suitableterminal fittings for connection with lead wires.

A channel-shaped bar 15 overlying the shaft assembly extends between andhas its opposite ends secured to the frame plates 3|--32. This bar isprovided with a series of paired slots 18, one pair for each commutatorassembly, the slots of each pair being in alignment with a verticaldiameter aaaaus through its associated commutator. The bar 15 serves tosupport and position a commutator adjusting tool 11, shown in Fig. 7,the shank portion 18 of which is adapted to be inserted into andextended through a selected pair of slots 16 for engagement with acommutator ring assembly at the marginal recess 66, as shown in Fig. 3.As a means for directing the tool shank 18 to the lower slot after ithas been inserted into the upper slot, each pair thereof is providedwith a spring guide finger 19.

Describing now the manner in which the control unit is electricallyconnected to the motor 23, and with special reference to Flig. 8 it willbe noted that the contact rings are circuited with disc 53 through rods46 and conductors 4 8, the latter in reality being constituted by thecontact discs bearing the same designation. Also, the contact 36 throughconrings 4-4 are circuited with shaft ductors 4| the equivalent of thecontact discs similarly designated. The motor 23 may be of any suitablereversible type, for simplicity shown as having a winding 80 connectedat one end to shaft 36 through a conductor 81, the equivalent of aground connection. The opposite end of winding '0 is connected by aconductor 82, to contact spring 1! v that engages disc 53. Winding 60has a centerterminal 83 which is connected to one 01' a pair of powersupply lines 84. The other power line is connected to the commonterminal wire 86 of a group of single-pole selector switches 86 whoseopposite terminals are connected, individually and respectively, to thecontact brushes 10 by lead wires 81. The selector switches 86 arepreferably provided with mechanical means (not shown), that operate toprevent more than one thereof from being closed at a particular time. Aswitch unit of this character is well known in the art and in effect, isthe equivalent of a multi-throw switch. The selector switches 86 may bemounted on the control panel of the radio receiver, or, if desired, maybe separated therefrom wtih connections made through a suitable multiplewire cable, .thus providing for remote control of the instrument.

To pre-set a commutator ring of the pro-selector unit 30 so thatactuation of the particular switch 86 circuited with that ring willcause the receiver to become tuned to a desired transmitting station,the following procedure is used. The tool 11 is inserted through theappropriate pair of slots 16 and the 30 is turned as by manual knob 22,to bring the recess 66 of the selected commutator ring into registrationto enable the tool shank to enter the said recess. Thus, the commutatorring becomes locked in such position, shown in Fig. 3, that itsassociated brush 10 bears upon the insulating materiol in the gap 63,being out of electrical contact with both of the ring elements 44 and5|. Now, with the receiving apparatus conditioned for operation, knob 22is manipulated to tune the instrument to the signal frequency of thedesired sending station. Since the selected commutator ring istemporarily looked as previously described, it cannot turn with thetuning condenser and other rotatable parts of the unit 3|. Accordingly,the selected commutator ring is given a definite angular setting withrespect to that position of the condenser which tunes in the desiredtransmitting station. The tool 11 may now be removed and used in thedescribed manner for effecting thesetting of the other commutator rings.

The described apparatus functions in the following manner to tune indesired stations. Re-

, instantaneously entire rotor assembly of unit fer-ring to Fig. 7,wherein letters are attached to the reference numerals of correspondingparts to distinguish the several commutator circuits from each other,assume that a station identified with the selector switch 88a isdesired. Such switch is closed to complete the electric circuit throughconductor 81a,.oontact brush 10a, commutator ring element Ma, contactdisc a, rods 46, disc 53, brush 1|, right hand portion of the motorwinding 80, and back to the power supply lines '84. Motor 23, thuslyenergized, turns the rotor assemblies of the condenser and control unitin a clockwise direction until the circuit becomes broken by reason ofthe contact end of brush 10a. riding oil of the ring element Ma at thegap 680. The commutator ring will then be in its pre-set position,corresponding to a position of the condenser rotor that eflects accuratetuning of the desired station identified with selector switch 860.Because of its relatively low speed and low inertia, the compound rotororganization stops almost when the circuit is broken at gap 66a, butshould the brush ride over this gap and contact with ring element a,motor 23 will become reenergized in a reverse direction, being circuitedthrough ring element 44a, contact disc a, shaft 36, ground connection8!, and the left hand portion of the motor winding 80. However, byproperly proportioning the size of the gaps 63a, etc., and the contactends of brushes 16a, no so-called hunting will occur.

The control unit herein described is adapted for use with condensers ofprevalent type which have a tuning range of approximately 180 degrees.When the commutator rings are properly pre-set, their marginal, orlocking slots 66 will remain at all times in the uppermost hemi-circleand cannot become engaged by the brushes 10.

From the foregoing description it will appear when one of the selectorswitches '86 is closed, the motor 23 operates under the control of thecommuntator ring associ ated with that particular switch until theselected station is tuned 1n.

Having described my invention with reference to a single presentlypreferred embodiment thereof, it will be understood that various changesmay be effected without departing from the spirit and full intendment ofthe invention which is defined by .the appended claims.

I claim:

1. A preselector switching mechanism of the character described,comprising a frame, a shaft journalled in said frame, a plurality ofcommutator assemblies, each including an insulating hub fixed to saidshaft, 8. pair of relatively insulated, axially spaced conductor discs,a commutator ring mounted for angular adjustment on said hub betweensaid discs, said ring including a pair of contact segments separated byan insulating gap, each of said conductor discs bearing laterally on oneof said contact segments, means electrically interconnecting oneconductor disc of each switch assembly, means electricallyinterconnecting the remaining conductor discs, a plurality of brushesmounted on said frame, each coacting with one of said commutator ringsto make electrical contact with the commutator segments individually andadapted to break such contact at said insulating gap, and means fortemporarily locking each commutator ring to the frame to facilitateadjustment of the angular setting thereof relative to said shaft.

2. A preselective control device of the character described, comprisinga rotatable metal shaft, a

plurality of commutator assemblies, each including an insulating hubfixed to said shaft, a commutator ring frictionally retained on saidhub, adapted for angular adjustment relative thereto, and comprising apair of relatively insulated conducting segments, a pair of conductingdiscs flanking said commutator ring, each bearing laterally on one ofsaid segments, one of said paired discs being mounted on said hub andin- 10 sulated thereby from the shaft, and the other of said paireddiscs directly engaging said shaft; a conducting rod extending throughaligned apertures in said discs, means connecting said rod to thehub-mounted discs, means insulating said rod from the shaft-engagingdiscs, 9. contact ring and brush assembly communicating with said rod,and an individual brush for each commutator ring, adapted alternately toengage the segments thereof.

BYROM J. SMITH, JR.

